This study represents an attempt to apply ethological methods of observation and analysis to human infant behavior. It is a study of social structure and behavior of peer groups of communally-reared children ranging in age from birth to 48 months, living in the Synanon School. During the period from January-September, 1974 a total of over 5,500 agonistic interactions were recorded. The results indicated that a stable and linear dominance hierarchy existed for this age range. There were no sex differences in frequency of aggression or submission. A total of 65 separate categories of aggression and 37 categories of submission were delineated. The rank of the child was not significantly correlated with frequency of aggression, age, or size. Correlations of dominance and aggression with other variables revealed a significant positive correlation with social maturity, a significant negative correlation with hyperactivity, and a significant positive correlation with intelligence.